Interventional catheter assemblies and control systems

ABSTRACT

An interventional catheter assembly has an operating head [ 400 ] and catheter system [ 300 ] that are inserted and navigated within a patient&#39;s body while an operator controls the system externally of the operating head. Fluidic communication is provided between the operating head and the external system controls, and rotation is provided to the operating head by means of an external drive system. Numerous system controls are provided, along with various operating systems, sealing assemblies, actuators, torque transfer systems, and the like are provided. Some systems and controls are provided in a control pod [ 200 ] and some controls, as well as displays, are provided in a console unit [ 100 ]. Control pod [ 200 ], catheter system [ 300 ] and operating head [ 400 ] may be provided as a sterile, single use interventional catheter system, while the console unit [ 100 ] may be provided as a multiple use device that communicates with the sterile, single use interventional catheter system during operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. patent application 60/453,846filed Mar. 10, 2003. The disclosure of this application is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to systems for removing material, such asobstructions and partial obstructions, from an internal lumen or cavityof a mammalian subject, such as a blood vessel, a portion of thegastrointestinal tract, dural spaces, and the like. More particularly,the present invention relates to interventional catheter assemblieshaving mechanisms for advancing and/or rotating an operating head at atarget material removal site, aspirating fluid and debris from a targetremoval site, infusing liquid and debris from a target removal site, andcontrol systems for use with such interventional catheter assemblies.

BACKGROUND

Removal of disease such as atherosclerotic plaque, thrombus, and othertypes of obstructions and partial obstructions from internal body lumensor cavities is a well-established interventional technique. Numerousinterventional catheters have been conceived and developed. Most ofthese systems require placement of a guiding catheter and guide wireprior to introduction and placement of the interventional catheter atthe target operating site. Advanceable and/or rotating operating headshave been used to cut and/or ablate obstructions. Many of these priorart systems incorporate aspiration systems to remove the ablatedmaterial from the site.

Despite the many and varied approaches to material removal systems, manychallenges remain in providing systems for removing material from alumen, such as a blood vessel, safely and reliably and without causingcomplications. The safety and reliability of the system is manifestlycritical. Recovery of debris generated during a material removaloperation, or maceration of the debris to a particle size that will notproduce blood vessel damage or embolic events is essential. Theflexibility and size of an interventional catheter is also an importantfeature. The system must be small enough and flexible enough to navigatethrough sometimes tortuous internal structures and passageways, such asblood vessels, for placement at the target interventional site. Theinterventional catheter must also have sufficient stiffness andintegrity to operate reliably at high rotational rates while allowingfor aspiration and/or infusion of fluids to the site.

In interventional catheters that employ a “cutting head,” any cutterstructures must be benign during navigation of the operating head to andfrom the target site, yet effectively remove material during theoperation. In addition, cutter structures must effectively removedisease or undesired material without damaging delicate neighboringtissue, such as blood vessel walls or other healthy tissue, which oftensurrounds the undesired material. Thus, it is important for cutterstructures of the interventional catheter to accurately and reliablydifferentiate between the disease or undesired material and healthytissue.

The extent and consistency of the disease or undesired material formingan obstruction are frequently not well characterized prior to anintervention. Thus, although interventional catheters and cutterassemblies having different sizes and material removal properties may beprovided, and may even be interchangeable on a material removal system,it is difficult to ascertain which combination of features will be mosteffective in any particular intervention prior to insertion of thedevice. Various quick-connect systems have been developed to permitremoval and installation of multiple operating catheters during a singlesurgical intervention. This is not ideal, since the interchange,requiring withdrawal and insertion of multiple interventional catheters,is time consuming and increases the risk of the operation. Having accessto multiple cutter assemblies having different sizes and differentmaterial removal properties on a single interventional operatingcatheter is highly desirable.

Many prior art interventional catheters are intended to be entirelydisposable. That is, the catheter tube, operating head, drive andcontrol mechanisms are provided as sterile, single use, disposablesystems. Because such systems have rigorous operating and controlrequirements, providing an interventional catheter and control assemblyas a single-use, disposable system is expensive. It would be desirableto reuse some of the operating and/or control mechanisms withoutsacrificing sterility and operational convenience.

Several prior art interventional catheters provide for aspiration ofliquids and/or debris from the material removal site. In general, suchaspiration is provided by a vacuum pump or, in many cases, by anevacuated recovery vessel, such as an evacuated bottle. These systemstend to provide inconsistent and variable vacuum during operation, whichreduces the efficiency and effectiveness of the material removaloperation and, under certain circumstances, may compromise the health ofthe patient.

The operation of an advanceable, rotatable operating head is generallyunder the control of a physician or other professional using some typeof a sliding advancement mechanism operated within the sterile field.Advancement of a rotatable operating head to remove undesired materialmust generally be carefully coordinated with rotational control of theoperating head. Rotational speed displays may be provided in the form ofan rpm gauge on a control module. Advancement of the operating head isoften visualized on a separate display.

Although interventional catheters are used frequently, limitations inthe flexibility, reliability and versatility of existing systems limitthe types of disease conditions that can be effectively treated. Theinterventional catheter assemblies and control systems of the presentinvention have been designed to overcome these limitations.

SUMMARY OF THE INVENTION

Interventional catheters of the present invention incorporate anoperating head mounted at or near their distal ends to cut or abrade orotherwise break down undesired material at a target intervention site.The operating head may have cutting surfaces or blades, such as a cutterassembly having one or more differential cutting surfaces. Although the“cutting” surfaces or blades of interventional catheters of the presentinvention may be sharp and may actually “cut” material at the targetsite, the term “cut” or “cutting,” as used herein, refers to cutting,scraping, ablating, macerating and otherwise breaking down undesiredmaterial into removable particles or smaller, removable units ofmaterial. “Cutters,” “cutter assemblies,” “cutting surfaces” and“blades” likewise refer to structures for cutting, scraping, ablating,macerating and otherwise breaking down material into smaller pieces. Theoperating head is operably connected to a rotatable and axiallytranslatable drive shaft, drive system, aspiration source, and variouscontrol systems.

As used herein in the description of various components, “proximal”refers to a direction toward the system controls and the operator alongthe path of a drive system, and “distal” refers to the direction awayfrom the system controls and the operator and toward or beyond aterminal end of the cutter assembly. In one embodiment of aninterventional catheter assembly of the present invention, a cutterassembly comprises at least one differential cutting surface positionedat or near the distal end of the interventional catheter system.

Interventional catheters of the present invention preferably include anaspiration system for removal of debris from the intervention site,generally via aspiration through one or more material removal ports inthe cutter assembly or another component in proximity to the cutterassembly. Debris generated during a material removal operation isremoved by aspiration through the material removal ports and withdrawnthrough a sealed lumen of the interventional catheter. The sealed lumenis connectable to a vacuum source and aspirate collection system. Thematerial removal ports may be disposed between blade surfaces of thecutter assembly.

Liquid infusion may be provided in proximity to the cutter assembly inaddition to or alternatively to aspiration. Infusion of liquids may beused to provide additional liquid volume for removal of debris, or todeliver lubricating fluids, treatment agents, contrast agents, and thelike. Infusion of fluids in proximity to the area of a material removaloperation may be desirable because it tends to reduce the viscosity ofthe materials being removed, thus facilitating removal throughrelatively small diameter lumens. Infusion of liquids also desirablytends to reduce the volume of blood removed during the operation.According to one embodiment, a sealed lumen formed between the cutterassembly drive shaft and a catheter may alternatively and selectively beused as aspirate removal system and an infusion system. The sealed lumenmay thus be selectively connectable to a vacuum source and aspiratecollection system for aspiration, and an infusion source for infusion ofliquids. Ports in or in proximity to the cutter assembly may be thus beemployed, selectively, as aspiration and infusion ports.

Interventional catheter assemblies of the present invention incorporatevarious control systems that, in combination with other features,provide enhanced system efficiency, reliability, versatility anduseability. In one embodiment, the interventional catheter assemblycomprises a control module that is reusable and operates outside thesterile field in combination with a control pod in which theinterventional catheter is mounted. Using this system, expensive andheavy system components and controls can be centralized in the controlmodule, which is isolated during operation, and reused.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features of the interventional catheter assembly of the presentinvention are illustrated by way of example in the figures describedbelow. The figures and detailed description of various aspects of theinvention are not intended to limit the generality of many aspects ofthe present invention.

FIG. 1 is a schematic diagram of an interventional catheter assemblycomprising an operating head mounted at or near a distal end of acatheter system, a control pod and a console unit, according to oneembodiment of the present invention.

FIG. 2 illustrates the control and display features of a console unit ofthe present invention.

FIG. 3A illustrates a certain control and operational features of acontrol pod of the present invention.

FIG. 3B illustrates a sliding actuator button.

FIG. 4 illustrates an enlarged, exploded perspective view of a sliding,rotatable torque transmission system of the present invention.

FIG. 5 illustrates, schematically, a fluid seal system for preventingair ingress to the catheter system.

FIGS. 6A and 6B show enlarged, cross-sectional views of variouscomponents of a fluid seal system of FIG. 5.

FIG. 7 shows an enlarged perspective view of an extendable guidewiresupport of the present invention.

FIG. 8 shows an enlarged perspective view of a sliding, liquid-tightconnector used in the interventional catheter assembly of the presentinvention.

FIGS. 9A and 9B are fluoroscopic x-ray images of a coronary arteryhaving a removal site, wherein FIG. 9A depicts the nearly totally anddiffusely occluded artery before the operation of the removal system andFIG. 9B depicts a cleared artery after use of the interventionalcatheter assembly of the present invention.

FIG. 10 shows the results of an experimental laboratory simulation inwhich an artificial lesion was treated using an interventional catheterof the present invention and both aspirated and non-aspirated(embolized) particulates were collected, quantified and sized.

DETAILED DESCRIPTION

Interventional catheter assemblies and control systems of the presentinvention are suitable for use within any body lumen or cavity that hasa sufficiently open space to accept the operating head and is suspectedof containing undesirable material. Body lumens and cavities in whichsuch interventional catheters may be used include blood vessels andvascular cavities, gastrointestinal cavities, lumens or cavities in maleand female reproductive organs, other fluid cavities such as gasexchange cavities, nasal and sinus cavities, and the like. The lumen orcavity may be a generally tubular-shaped structure, such as bloodvessel, or another lumen structure, such as a ureter, a fallopian tube,a nasal passageway, and other tubular passageways. For example, systemsof the present invention may be used for removing undesired materialfrom native blood vessels such as native coronary, renal, cranial,peripheral and other blood vessels, artificial or grafted vessels suchas saphenous vein grafts, and the like. The body cavity may also bewithin or in proximity to an organ, such as a kidney, gall bladder,lung, or the like, or the body cavity may form part of another system,such as a lymph node, spinal canal, etc. Interventional catheters aregenerally used with mammalian subjects, particularly human patients. Theundesired material that is removed using interventional catheterassemblies and control systems of the present invention may be diseasematerial such as atherosclerotic plaque, calcified plaque, thrombus,gallstones, a valve or portion thereof, and the like.

The present interventional catheter assembly includes an operating headand catheter system that are inserted and navigated within a patient'sbody while an operator controls the system externally of the operatinghead and catheter system. Fluidic communication between the operatinghead and externally positioned components of the system is generallyprovided by one or more sealed passageways of a catheter system. Othertypes of communication systems or pathways may also be provided fordelivery of power, control features, and the like. The operating headmay be driven, or controlled, using electrical systems, radio frequencyand other remote forms of control systems, mechanical systems, magneticsystems, and other systems or mediums that are in use now or may bedeveloped in the future for remote operation of an operating head. Thesystem components described below are described as exemplary componentsand are not intended to limit the scope of the invention.

Exemplary operating heads, cutter assemblies and blades, bearings,components, and subassemblies suitable for use in connection with theinterventional catheters and control systems of the present inventionare disclosed and described in publications incorporated herein byreference, including U.S. Pat. No. 6,565,588B1 and PCT PatentPublication WO 01/76680, and numerous other patent publications. Thecomponents, subassemblies and control systems of the present inventionmay be used with interventional catheters having any type of operatinghead. Operating heads having advanceable, rotatable cutter surfaces atnear their distal ends are especially suitable for use with theinterventional catheter and control systems of the present invention.The operating head is provided at or near a distal end of theinterventional catheter and is guided to and from a desired materialremoval site through internal passages, such as blood vessels, as iswell known in the art. At the target removal site, the operator head isactuated remotely by the operator to cut, grind or ablate, or otherwiseseparate and break down or remove undesired occlusive material. In manyembodiments, the occlusive material is removed the site by means of anaspiration system or another debris removal system.

The interventional catheter system is generally used in conjunction witha flexible guidewire that is navigated through internal pathways, suchas blood vessels, to a target material removal site. For partialobstructions, the guidewire is generally placed across the lesion andthe operating head of the interventional catheter is advanced, on theguidewire, to the target site and then into and through the lesion. Whena lumen is totally obstructed and a guidewire can't penetrate theobstruction without causing harm to nearby tissue or riskingembolization, the operating head may be advanced beyond the distal tipof the guidewire and into and through the obstruction, or the operatinghead and guidewire may be advanced in tandem. Although a guidewire is aconventionally used steering system for interventional catheters, othermethods for guiding and steering the operating head may be used, such asradio frequency systems, stereotactic systems, magnetic systems, remotecontrol systems, and the like. Interventional catheters may be adaptedfor use with any of these steering systems.

FIG. 1 depicts an exemplary embodiment of an interventional catheterassembly and control system of the present invention. In general, anoperating head 400 is provided at or near the distal end of a cathetersystem 300 for insertion into a body and navigation to a target materialremoval site. The catheter system 300 is operably coupled to theoperating head 400 at or near a distal end and to a control pod 200 ator near a proximal end. A drive shaft may also be operably coupled tothe operating head at or near a distal end and operably coupled to adrive system housed within control pod 200. The drive shaft may beprovided in association with one or more sealed conduits and/or layersproviding withdrawal of liquids and debris from the target site ordelivery of liquids to the target site, as is known in the art. Controlpod 200 houses operational and/or control components, such as a drivesystem, a system for translating torque from a motor drive to the driveshaft when a motor drive is used, a system for actuating and/oradvancing the operating head, a guide wire clamp, one or more connectorsfor conduits, and/or operator controls. A slidable drive motor actuator220 may optionally be provided coupled to the catheter system and theoperating head drive system to control operation and/or advancement ofthe operating head.

Various communications pathways, such as liquid and/or electricalconduits, extend between the control pod 200 and a console unit 100 thathouses various operating and control systems. A liquid conduit forcollecting debris and liquid during operation of the operating head isin communication with a liquid receptacle 90, for example. A liquidinfusate source may also be provided to provide fluid to the system,when desired. Console unit 100 incorporates various controls anddisplays and houses a vacuum or aspiration motor 102. Console unit 100may also provide a power source for operating the operating head andsystem components, or it may be in communication with an external powersource.

An exemplary console unit 100 is shown in more detail in FIG. 2. Varioussoftware components, e.g. applications programs, may be provided withinor in communication with the console unit, that cause a processor orother components to execute the numerous methods employed forcontrolling operation of the interventional catheter. The software maybe provided in a machine-readable medium storing executable code and/orother data to provide one or a combination of mechanisms to processuser-specific data, according to one embodiment of the invention.Alternatively, various systems and components may be controlled usinghardware or firmware implementations. Data storage and processingsystems may also be provided in console unit 100.

One function of the console unit is to provide feedback of system orenvironmental conditions or operating parameters. The console unit mayoutput operational information concerning operating conditions andfeedback from the material removal site to the operator. According toone embodiment, the console unit provides continuously updated output toan operator of operating parameters such as cutter head rotation rate,which may include the actual run speed as well as the desired speed;advance rate; aspiration rate and/or volume; infusion rate and/orvolume; length of the body or matter to be removed that is traversed;and the like. In one embodiment, a fluid flow sensor, such as a Dopplerdevice, may be also included in the system and fluid flow at the targetsite may be monitored and displayed.

Certain automated and selectable control features may be implemented inconsole unit 100. Preset routines or programs involving variousoperating parameters may be preselected, stored and selectable by anoperator, for example. Thus, according to one embodiment, a materialremoval system of the present invention implements control featuresbased on an operator's input of specified parameters. Specifiedparameters may include, for example: lesion length, lesion type andcharacter, such as calcified, fibrotic, lipid/fatty, and the like;and/or historical factors, such as restenosis; rate of blood flow;volume of blood flow; percentage of restriction; lumen type and/orlocation; lumen diameter; desired rotation rate and/or rotation profilefor the cutter assembly; desired advance rate and/or advance profile forthe cutter assembly; desired aspiration rate and/or profile; desiredinfusion rate and/or profile; and the like. Based on the specifiedparameters input by the operator, an automated cutter assembly controlunit may calculate and implement automated operating conditions, suchas: cutter assembly rotation rate and profile; cutter assembly advancerate and profile; aspiration rate and profile; infusion rate andprofile; cutter assembly size and type; and the like. Various systemoperating parameters may also be recorded and stored duringinterventions to preserve a record of the operational parameters.

Aspiration pump 102 may be provided in association with console unit 100and, in this embodiment, console unit 100 is preferably provided as areusable system component. High efficiency aspiration is important inthe interventional catheter systems of the present invention. Aspirationpump 102 is preferably capable of providing constant, high levels ofaspiration of liquids and/or liquid/debris mixtures, at rates of atleast 15 ml/l through small catheter systems when the aspiration site isremote. In exemplary interventional catheter systems of the presentinvention, for example, the aspiration site may be more than a meteraway from the control pod through an aspirate removal passageway havinga diameter of less than 0.10 inch and more often between about 0.050 to0.070 inch, and more typically about 0.065 to 0.066 inch. The distancethat aspirate travels between the control pod and the console unit maybe from about 0.4 to several meters, through an aspirate conduit that isbetween about 0.125 to 0.94 inch in diameter. The blood and debris beingaspirated are relatively viscous fluids. Achieving a relatively constantand high level of aspiration under these conditions is essential.

In one embodiment, aspiration pump 102 comprises a multi-lobed rollerpump. At least three rollers, or lobes, are preferably incorporated inthe roller pump. The rotation rates of multiple rollers or of amulti-lobed rotating structure may be variable or selectable to controlthe aspiration rate and volume. Roller pumps permit fluid to flow inconduit through the rollers of the pump at atmospheric pressure, andthus reduce or prevent the formation of bubbles and foam in the liquidbeing evacuated. Because the aspirate is at atmospheric pressure when itexits the roller pump, a simplified, atmospheric pressure collectionvessel may be used rather than an evacuated collection vessel. A simplebag or another collection vessel, such as those used for collection ofblood, may be used. Collection bag 90 may be provided having a sealedconduit that is mounted in the roller pump and connected to an aspiratewithdrawal site at the control pod during operation. In this embodiment,the aspirate collection bag and sealed conduit may be provided as partof the sterile disposable interventional catheter system and simplymounted on the aspiration pump prior to operation.

In another embodiment, the aspiration pump may comprise multiple vacuumpumps aligned in series to provide a consistent and high level ofaspiration. In this manner, each pump incrementally increases pressurewhen it is operated in conjunction with other pumps in the series.Alternatively, the aspiration system may comprise multiple series ofpumps connected in parallel. This system may also provide a consistent,high level of aspiration.

Console unit 100 may house a power source or provide communication to anexternal power source. In the embodiment illustrated in FIG. 2, anelectrical device port is provided for providing electrical power to thecontrol pod. An electrical conduit may be provided mounted to electricalcomponents in the control pod and connected to the console unit prior tooperation. Console unit 100 also has a power on/off switch that controlspower to the device port.

In addition, console unit 100 may include control status indicators toshow the status of various system components and/or controls. Forexample, one or more operating head status indicators may show thereal-time status of the operating head. In the console unit of FIG. 2,for example, an operating head status indicator 104 shows whether theoperating head is at a minimum or maximum diameter during any operation.Console unit 100 also has a speed gauge 106 to display that actualrotational speed of a rotating operating head during operation. Ananalog gauge may be provided, as well as a digital gauge that shows thenumerical value of rpm. The rotational speed of the operating headchanges in real time to reflect the actual operating head speed as it isadvanced through an obstruction. Console unit 100 may also have controlswitches for activating and shutting down the aspirate withdrawal pumpand system, and for activating and shutting down an infusate system.These control features are generally provided as simple switches, thoughselectable levels of aspiration and/or infusate may be provided. Consoleunit 100 may also be provided with a timing mechanism that determines,and displays, the elapsed time of operation of the operating head and/orthe aspiration system. The volume of aspirate withdrawn may also bedisplayed.

Console unit 100 may also be provided with one or more selectable torquefeatures. The selectable torque features permit an operator to determinethe torque, or power, delivered to the operating head separately fromthe rotational speed and thus provides an additional level of operatorcontrol and safety. In an operating head having cutting blades, forexample, operation of the cutter assembly at a high torque setting mayprovide overly aggressive removal of undesired material and damagehealthy tissue. Some lesions that are composed of very hard material mayrequire operation at a high torque setting, and some cutter assembliesdo not damage healthy tissue even when operated at a high torquesetting. It is therefore highly desirable and increases the versatilityof the interventional catheter system to provide selectable torquelevels for operating the operating head. The selectable torque controlfeatures may be provided at the console unit, as shown, or they may beprovided at the control pod.

Selectable torque control features may be provided by limiting thecurrent provided to the operating head drive system. In one embodiment,for example, a maximum torque or power control setting 110 allows apreselected current level, such as 1.1-1.5 amps, to be provided to theoperating head drive system. A medium torque or power control setting112 may provide a preselected current level of from 0.7-1.3 amps to thedrive motor system. A minimum torque or power setting 114 may provide apreselected current level of less than 1 amp to the drive system. In acontrol system having selectable torque features, an additional overridecontrol feature may be provided. In this system, control circuitry isprovided so that when the current level required to maintain a desiredrotational speed at the operating head exceeds a predetermined value,power to the operating head is inactivated and the operating headstalls. If additional power is required to remove obstructive material,the torque setting may be changed and the operating head activated andadvanced into the lesion at the higher torque setting. Differentpreselected torque override values may be applied to each of theselectable torque settings and, if the system is programmable, may bechanged by an operator prior to use. A torque or power gauge may beprovided as an analog or digital gauge on the console unit or controlpod to show the actual torque delivered to the operating head as currentdrawn by the motor drive system The selectable torque control featuregreatly enhances the versatility and safety of the interventionalcatheter assembly.

In one embodiment, console unit 100, including aspiration pump 102, isprovided as a separate, re-usable unit. The console unit may thereforebe purchased as standard equipment in operating rooms, for example, andthe interventional catheter assembly comprising the control pod, thecatheter system and operating head may be provided as sterile, singleuse systems. In the systems illustrated, the console unit isn'tcontaminated by contact with blood or aspirate during operation, thepower and control systems are durable and long-lasting, and so theconsole may be reused for many interventions. The console unit may beprovided in a housing designed to sit on a platform during operation, orthe housing may be designed for mounting on a structure, such as an ivpole or another structure during operation. An aspirate collectionvessel may be mounted to the console during operation, or to anassociated structure. Similarly, an infusate source may be mounted tothe console or to an associated structure. In another embodiment, atracking pod and motor activation button may also be provided as areusable unit.

The control pod 200 is illustrated in more detail in FIG. 3A. Controlpod 200 is optionally electrically connectable to a power source, suchas an electrical power source at or in communication with console unit100. Control pod 200 is also in fluid communication with aspiratecollection vessel via a fluid conduit, and the drive shaft, aspirationconduit and catheter system all traverse and/or exit from control pod200, for example, at a distal end of the pod. Control pod 200 isconstructed from a durable, sterilizable material, such as hard plastic,and may be provided in any convenient ergonomic design and constructedfor placement in proximity to and/or in contact with the external body.In one embodiment, the control pod may include an integrated handle orsupport 202 for convenience in holding and supporting the control podduring operation. The control pod is preferably compact and may have agenerally triangular configuration, as illustrated in FIG. 3A.

The control pod, as shown, is intended to be used within the sterilefield during operation and is provided as part of the interventionalcatheter assembly. It will be noted, however, that some of the controland operational features of the control pod may be provided in theconsole unit and, likewise, some of the control and operational featuresof the console unit may be provided in the control pod.

In the embodiment of FIG. 3A, control pod 200 houses a drive motorproviding torque and rotation to the drive shaft and operating head. Thedrive motor may be of many types, such as electrical, pneumatic, or thelike. Electrical, direct current variable speed drive motors arepreferred for use in interventional catheter assemblies of the presentinvention because they reliably provide high power and high torque, yetnumerous control systems can be implemented. Preferred drive motorsdeliver a constant voltage source for any given rotational output. If,under load conditions, the voltage employed to produce a givenrotational output isn't sufficient, the motor system adjusts currentdelivered to the system to achieve the desired rotational output. Thevoltage delivered to the drive system is thus regulated according to thedesired rotational output. In preferred embodiments employing selectabletorque features, the current delivered to the drive system is regulated,and limited, by the torque selection. Preferred motor systems employcascaded variable regulator voltage sources. The motor system mayprovide bidirectional output.

The rotational output of the drive motor is preferably adjustable by theoperator to control rotation of the operating head. Rotational speed ofthe drive motor, drive shaft and operating head may be adjusted atcontrol pod 200 at speed up and down controls 206 and 208. In manyinterventional catheter applications, the drive shaft and operating headare rotated at high speeds. For example, rotational speeds of fromseveral hundred to 100,000 or 200,000 rpm may be required. When thedrive motor provides bi-directional output, a direction of rotationselection may be provided at the control pod. Similarly, if theoperating head operates in more than one configuration, an operatinghead selection may be provided at the control pod. In a preferredinterventional catheter assembly of the present invention, the operatinghead comprises a cutter assembly that is adjustable between a smallerdiameter and a larger diameter condition. A selection switch for tipsize may be provided at the control pod. Tip size may be controlled bychanging the direction of motor drive rotational output.

Delivery of rotation to the operating head drive shaft from the motoroutput shaft is important in interventional catheter assemblies thathave advanceable, rotatable operating heads, and must be accomplished sothat the drive shaft is simultaneously advanceable and rotatable.Mounting of the operating head drive shaft off-axis with respect to theoutput shaft of the motor drive using suitable gearing systems permitstranslation and advancement of the drive shaft independently from thedrive system, which allows the drive system to remain stationary duringoperation of the interventional catheter.

In one embodiment of a torque transfer system of the present inventionshown in the exploded view of FIG. 4, a torque transfer sliding tubesystem 620 may be provided for transferring torque to the drive shaft.The torque transfer system both provides torque to the drive shaft andpermits smooth axial translation of the drive shaft, even at highrotational speeds. The sliding tube torque transfer system also allowsthe catheter system to advance over a guidewire without the drive shaftdisengaging from the motor drive assembly and while a guide wire lockingdevice maintains the guide wire position. Experimental work has alsodemonstrated that the sliding tube torque transfer system of the presentinvention may provide an operator greater and more realistic tactilefeel for safe and effective removal of undesired material duringoperation of the operating head as the lesion when a sliding tube torquetransfer system is used in the interventional catheter assembly.

Sliding tube torque transfer system 620 comprises a rigid inner tube orcylinder 622 and a rigid outer tube or cylinder 624 that is axiallyslidable over at least a portion of the inner tube. Each of the tubes isprovided with at least two matching slots 632, 634 generally arranged ina radially symmetrical arrangement, with a ball bearing 628 beingslidably retained between each set of slots. The inner and outer tubesare sized so that when a ball bearing is placed between each of thematching slots, the tubes are both axially slidable and rotatable withrespect to one another. Slots 626 preferably extend for most of thelength of inner tube 622, so that the inner and outer tubes are slidablewith respect to one another along most of the length of inner tube 622.The slot of the outer tube usually extends through the body of the tubeand does not include a bottom surface. A proximal end of the outer tubemay be operably coupled to a pinion shaft 630 of the drive system. Thepinion shaft 630 transfers torque to the outer tube and retains the ballbearings. The pinion shaft 630 includes at least one gear 632 tooperatively couple to a drive system gear. Rotational torque istransferred from the pinion shaft, to the outer tube and, through theball bearings being positioned in the aligned channels, to the innertube and then to a drive shaft. The catheter system may be mounted tothe inner tube, such as through a main shaft 634, which allows smoothtranslation of the catheter even during high rotational operations.

Control pod 200 also includes a system for preventing gases, such asair, from being drawn into structural elements that move relative to oneanother and into the catheter system. Preventing air leakage into thesystem and preventing any resulting loss of pressure in a high vacuumzone is especially important in catheter systems employing highaspiration rates and requiring relatively high vacuum levels toeffectively aspirate fluids and debris from the material removal site.In one embodiment, a liquid seal is established in proximity to therotating drive shaft. This system is illustrated in FIGS. 5 and 6A-6B.

FIG. 5 shows a schematic diagram of the drive system in communicationwith a liquid seal system of the present invention. Control pod 200generally houses a drive system 8 that rotates a proximal end of driveshaft 10. The drive shaft 10 then passes through sealing assembly 4including a high vacuum section and is operably coupled to drive shaft10. A catheter system 6 surrounds the drive shaft and extends distallyto the operating head, enclosing the drive shaft and providing aspirateand/or infusion lumens. The sealing assembly utilizes a drive shaftliner and takes advantage of pressure differentials within the controlpod to produce a liquid seal that prevents ingress of air into thecatheter system.

FIG. 6A shows one embodiment of sealing assembly 20 having a sealingmember 22 and a liner 24 wrapped around a drive shaft 26. The sealingmember includes a housing 28 enclosing one or more sealing sites. Thehousing is a rigid member that encloses at least a portion of the driveshaft in a manner that permits free rotation and axial translation ofthe drive shaft. The housing includes a longitudinal bore 30 throughwhich the drive shaft is positioned. The bore includes one or moreaxially aligned sites that form the one or more sealing/junction sites.At least one layer of the catheter system enclosing the drive shaftpasses into the sealing assembly at an aperture 32. The proximal end ofthe catheter system terminates in the sealing assembly in an aspirationzone 38. The drive shaft continues through the sealing assembly andpasses through an exit aperture, such as overflow port 56. Liquid isprovided to the sealing assembly at a region of substantiallyatmospheric pressure. This area is susceptible to leaking air to theneighboring low pressure aspiration zone. The liquid seal prevents airfrom traveling along a significant length of the drive shaft towards thematerial removal site. An infusion port 40 supplies reservoir 42 forretaining liquid during operation of the interventional catheter.

An, enlarged view of a portion of a liquid seal site 36 is shown in FIG.6B. In general, a tubular liner 24 is spaced apart from and surrounds atleast a portion of the longitudinal length of the drive shaft. The lineris generally not bonded to the drive shaft so that as the operating headis rotated, the drive shaft is rotate freely, while the liner remainsstationary. Surface tension and head loss prevent the liquid from movingvery rapidly into or very far along a flood space formed within theinside diameter of the liner, even when high vacuum levels are providedin the aspiration zone. Thus, only a minimal amount of liquid travelsthe flood space.

The liner may comprise any material that is formable into a thin, tough,flexible, sealed tube. The liner is typically highly compliant so thatit follows the contour of the drive shaft without reducing theflexibility of the drive shaft. The liner is supported along its lengthby the drive shaft, and the liner material therefore need not be stiffor resistant to changes in pressure. The material forming the liner mayalso be slippery, or lubricious, when wet or when contacting anothermaterial. The liner material also possesses high thermal resistance anddoes not degrade as a consequence of frictional loads created by driveshaft rotation. The liner may comprise conventional, polymer-basedtubing comprising, for example, a polyimide material and having alubricious surface coating, such as a polytetrafluoroethylene (PTFE),such as Teflon®, on at least the inner surface of the liner.

The dimensions of the liner depend, inter alia, on the diameter anddesign of the catheter system and drive shaft, the characteristics anddesign of the seal assembly, and the anticipated local vacuum levelsrequired to produce the desired level of aspiration. The clearancebetween the liner and the drive shaft at the flood space is typicallyquite small, such as about 0.002 to 0.003 inch. The wall thickness ofthe liner is typically very small, such as from about 0.001 to 0.0015inch. The liner extends a distance along the axial length of the driveshaft sufficient to prevent air leakage along the length of the liner.In an exemplary system, the liner may extend for about 1 to 30 inches inlength, more typically from about 6 to 25 inches in length. A longerliner is often desirable to minimize, due to head loss, the amount ofliquid traveling the flood space and exiting the distal end of the floodspace to dilute aspiration. In interventional catheters employing highaspiration rates, the liner may consume some of the available lumenspace for aspiration. Where high aspiration rates are desired,relatively shorter liner sections may be provided.

As the interventional catheter is operated, liquid continues to flowinto the sealing assembly from the infusion port. Typically, liquidflows from an external liquid source through tubing connected to theinfusion port. In one embodiment, liquid drips from a conventional fluidbag that is placed a distance above the sealing assembly and feeds thesealing assembly by gravity flow. Saline and water are common liquidsthat are suitable for use in the sealing assembly and are convenientlyprovided in a sterile form. In another embodiment, the liquid maycomprise blood and/or plasma that is withdrawn from the patient. Forexample, blood and/or plasma that is aspirated from the patient throughthe interventional catheter may be treated by filtration, mixed withagents such as anticlotting or treatment agents and then introduced intothe infusion port to provide liquid for the sealing assembly.

Control pod 200 may additionally house an extendable, telescopingguidewire support, which reduces the size requirements of the controlpod and provides guidewire support over a variable length. FIG. 7illustrates one embodiment of a guidewire support 250 comprising afolding assembly having aligned holes for passage of a guidewire. Eachpanel 252 of guidewire support 250 has substantially the samedimensions, has a guidewire passageway 254 in a location correspondingto guidewire passageways in the other panels, and is foldable along eachof its sidewalls with respect to adjacent panels. The guidewirepassageways are preferably sized to allow passage of guidewires having arange of diameters.

The guidewire support may be mounted at a proximal end to the motordrive or another structure within the control pod and may be mounted ata distal end to the guidewire brake or another structure within thecontrol pod. The guidewire support is adjustable between a shorter,substantially folded condition and a longer, substantially extendedcondition as the structures between which the support is mounted moverelative to one another. In one embodiment, the guidewire support isadjustable between a shorter, substantially folded condition in whichthe axial length of the guidewire support is about one inch or less anda longer, extended condition in which the axial length of the guidewiresupport is about 6 inches or more.

Control pod 200 may also incorporate a guidewire brake or locking device210, as shown in FIG. 3A, adjustable between a clamping position inwhich the guidewire is prevented from moving axially or rotatably and arelease position in which the guidewire freely passes through the brake,the control pod and the catheter system. The guidewire brake is open,for example, as the guidewire is navigated to and from a targetintervention site, while the guidewire brake is clamped after beingpositioned across a lesion as the operating head is advanced and/orrotated. Guidewire brake 210 may be manually operated or actuated byelectrical or electronic systems and preferably accommodates and iscapable of clamping and releasing guidewires having a variety ofdiameters. The guidewire brake may alternatively be provided external tothe control pod.

In one embodiment, the guidewire brake position is monitored, forexample using an electrical or optical device that senses whether theguidewire brake is in a clamped or a release position. When theguidewire brake is in a release position and the guidewire is freelymovable, a control system interrupt prevents the motor drive andaspiration systems from being actuated and, consequently, the operatinghead is not operable. The control system permits rotation andadvancement of the operating head when the guidewire brake is in aclamped condition. This control system interrupt ensures that theguidewire brake is appropriately clamped before the operating head isactuated.

For interventional catheter systems in which it may be desirable torotate the operating head, for example at low speeds during withdrawalof the operating head from the material removal site of the patient, aselectable interrupt override control 212 may be provided to permit anoperator to override the interrupt control and permit translation and/orrotation of the operating head while the guidewire is simultaneouslymoved. The selectable interrupt override control may be positioned inproximity to the guidewire brake on the control pod or remotely on theconsole unit, for example.

Associate with the control pod, as shown in FIG. 3B, is a slidable drivemotor actuator 220. The slidable actuator is slidable over cathetersystem 222 and is in operable communication with the operating head anddrive shaft drive system. The operable communication may be provided bymeans of an electrical conduit communicating between actuator 220 andthe drive system, or communication may be provided by wirelessmechanisms. In one embodiment, slidable drive motor actuator 220incorporates a switch 224 that, when actuated, such as by depressing abutton, activates the drive system and/or an aspiration system. When theswitch is released, the drive system and/or aspiration system areinactivated.

Slidable actuator 220 also incorporates a clamp mechanism that securelygrips the catheter system over which it is slidable when actuated. In apreferred embodiment, the clamp mechanism actuated and released by thesame switch 224 that activates the drive and/or aspiration systems. Inthis system, the sliding actuator may be freely translated along andrepositioned on the catheter system when the motor and/or aspirationsystems are inactivated. When the switch is actuated, such as by anoperator gripping the motor actuator between a thumb and finger anddepressing switch 224, the drive system and/or aspiration system isactuated and the catheter system, drive shaft and operating head may betranslated, e.g. advanced into or withdrawn from a target operating siteand operated to remove undesired material. After one or more operatingpasses through a lesion are made, the switch may be released, and theactuator may be repositioned on the catheter system for furtheroperating passes through a lesion or other material desired to beremoved. This system, providing convenient operator control of bothactuation and advancement of the operating head in a single controldevice, provides improved manipulation of the operating head and precisecontrol features.

A delay may be incorporated between the time the drive system andaspiration system are activated, such that the aspiration system may beactuated immediately upon actuation of the switch, while the drivesystem may be actuated after a predetermined or selectable delay period.The activation delay period allows the aspiration system to be operatingat full aspiration capacity prior to actuation of the drive system andoperation of the operating head. A delay period may also be incorporatedwhen the operating head is inactivated, such that the drive system isinactivated immediately upon release of the switch, while the aspirationsystem may be inactivated after a predetermined or selectable delayperiod. This inactivation delay period allows the aspiration system tocontinue operating for a short period after the operating head isinactivated to ensure that all debris is removed from the operatingsite.

Catheter system 300, exiting the proximal end of control pod 200, isaxially translatable with respect to the control pod 200 as theoperating head and catheter system are guided to a target materialremoval site. Flexibility of the catheter system is important, and thecatheter system must also have sufficient integrity to prevent collapseof the catheter system during aspiration. All or particular sections ofthe catheter system may additionally be constructed to providenon-kinking properties. Because the catheter system carries the driveshaft and aspiration and/or infusion lumens, it is essential that thecatheter system remain flexible and non-kinking during navigation to thetarget material removal site, and during operation of the operatinghead. In one embodiment, a non-kinking, noncollapsing catheter isprovided using a multi-layer construction in which a coil constructedfrom a rigid material, such as a metal, is interposed between and isconcentric with an inner flexible tube layer and an outer flexible tubelayer.

The coil is preferably only bonded to either the inner or outer flexiblelayers at one or both ends of the coil and the remaining portion of thecoil is free, so that as the multi-layer catheter is flexed, all of thelayers are capable of flexing independently of one another. The innerand outer tube layers may comprise any flexible tubular material, suchas polyimide, and may have a lubricious coating, such as a PFTE coatingon surfaces that contact the coil. In one embodiment, a thermallyshrinkable coating that is etched is provided. The coating is applied byshrinking a tube to 25 percent or less of the tube's original diameterprior to heating. The multiple catheter system layers are preferablysized to provide firm contact between adjacent layers and to allowsufficient internal space to provide the required internal lumen(s). Theouter flexible layer may be thicker than the inner flexible layer. Anon-kinking catheter construction may be provided along the entirelength of the catheter system, or along a portion of the length. Theportion of the catheter system that exits the control pod when theoperating head is positioned near a target site may be particularlyprone to kinking, and providing a multi-layer catheter construction ofthis type at the proximal end of the catheter system is especiallysuitable.

The catheter system is introduced to a body through an entry systemplaced to access an internal passageway, such as the femoral artery.Ports are provided in the entry system for passage of the cathetersystem. The catheter system may be introduced through the port and thentranslated through the port and guided to the target material removalsite. Clamps are generally provided for sealing against the cathetersystem after placement at the target site. Sealing against fluid leakagefrom the port is often problematic, however, as the catheter system isguided to the target site. The interventional catheter assembly of thepresent invention may incorporate a fluid-tight slip seal adapter in itsproximal region that slides over the catheter system to seal a connectorof the entry system through which the catheter system is guided into thebody from fluid leakage.

One embodiment of slip seal adapter 310 is shown in FIG. 8, in which atleast one catheter may be moveable, such as axially translated, relativeto a connector 320. The adapter is inserted within a conventionalconnector 320 to seal the catheter and a proximal terminal end of aguiding catheter 322. The adapter includes a rigid tube 312 and athermally shrinkable wrap 314 extending from the tube. A lumen 316 runsthrough the adapter to permit the catheter to pass through the connectorand through the adapter lumen, whereby the shrinkable wrap closelysurrounds a portion of the catheter. The shrinkable wrap comprises alubricious material, e.g. Teflon®, that permits the enclosed catheter tomove in a lateral and/or rotational direction and yet maintains theclose contact with the catheter. When the shrinkable material isprocessed, it tightly grips the tube of the adaptor insertion end, whilethe seal section extending beyond the adaptor insertion end is notsupported by the adaptor and shrinks to a diameter that is less thanthat of the adaptor. The inner diameter of the seal section generallymatches the outer diameter of the catheter system and, as a consequenceof the lubricious properties of the material, is slidable over thecatheter system. Thus, when the insertion end of the slip seal adaptorbody is positioned in a port of the entry system connector, the sealsection snugly contacts the catheter system and prevents leakage offluids such as blood, through the port of the entry system. Thisprovides a liquid-tight connection in the insertion system withoutapplying a clamping pressure that deforms or damages the cathetersystem.

Numerous tests have been conducted using the interventional catheter andcontrol systems of the present invention. For example, the systems havebeen used to treat acute coronary syndrome and acute myocardialinfraction in native coronary arteries. Furthermore, the systems havebeen used for preparing occluded saphenous vein grafts for accepting astent. Example 1, described below, shows images of blood vessels beforeand after a material removal operation, and Example 2 describeslaboratory tests demonstrating the aspiration efficiency of aninterventional catheter assembly of the present invention.

EXAMPLE 1

FIGS. 9A and 9B are fluoroscopic x-ray images showing the results ofusing an interventional catheter assembly of the present invention. FIG.9A shows a nearly totally and diffusely occluded artery having acoronary bypass graft. The patient was injected with an ionic contrastagent to visualize blood flow and blockages.

The interventional catheter system of the present invention is used toclear the obstruction, often followed by insertion of a stent. A guidingcatheter is inserted into the patient and a guide wire was directed tothe target site in the artery. The cutter is rotated at 35,000 to 40,000rpm's while aspirating at the target site. The cutter is advanced withlittle applied force into the lesion for 3 seconds at a rate of at 1 mmper second. The advancing movement is paused to allow cut particles tobe aspirated into the cutter assembly and then the advancing movement isrepeated. Contrast agent is applied to the area to visualize theintermediate results of the cutting and to decide on whether to use anexpanded diameter of the adjustable cutter on further passes into thetarget site. A stent is inserted at the target site. FIG. 9B shows thesame artery and coronary bypass graft of FIG. 9A, following removal ofobstructions using the interventional catheter assembly describedherein, followed by stenting.

EXAMPLE 2

FIG. 10 shows experimental results using the interventional catheterassembly of the present invention in a laboratory model of obstructiveheart disease. In the laboratory model, a 2 cm long lesion was simulatedin a blood vessel-like structure and a liquid having a viscosityequivalent to blood was circulated. Aspirated and embolized particulatematerials were collected as an interventional catheter system wasadvanced and rotated through the lesion. The size of the collectedparticulates was measured and the collected particulates werequantified. As shown in FIG. 10, particles of all sizes were effectivelyaspirated. FIG. 10 also shows that a large number of small particulateswere aspirated and only a small number of very small particulates werenot collected by the aspiration system and, in a clinical setting, maybe embolized. The interventional catheter assembly of the presentinvention, constructed as described herein produced an aspirationefficiency of 97%.

The present invention has been described with reference to specificembodiments and figures. These specific embodiments should not beconstrued as limitations on the scope of the invention, but merely asillustrations of exemplary embodiments. It is further understood thatmany modifications, additions and substitutions may be made to thedescribed interventional catheter and control system without departingfrom the broad scope of the present invention.

1. An interventional catheter assembly comprising: a. an operating headcoupled to a drive shaft and a drive assembly for rotation; b. acatheter system forming a sealed lumen mounted for axial translation ata proximal end with a control pod and communicating at a distal end withthe operating head; and c. a control pod housing operational componentsfor selectably rotating the operating head, wherein the control podhouses a drive motor operably coupled to the drive shaft and the drivemotor is coupled to an actuator slidably mounted on the catheter systemand positioned distally to the control pod and in operable communicationwith the drive system, wherein the actuator incorporates (i) a switchthat activates at least one of the drive system and an aspirationsystem, and (ii) a clamp mechanism that is actuatable to grip thecatheter system and releasable to allow translation of the actuatoralong the catheter system.
 2. An interventional catheter assembly ofclaim 1, additionally comprising an operating head drive motor coupledto the drive shaft, wherein the drive motor employs a cascaded variableregulator voltage source.
 3. An interventional catheter assembly ofclaim 1, wherein the control pod incorporates selectable operatoradjustment features allowing an operator to increase and decreaserotational speed delivered to the drive shaft.
 4. An interventionalcatheter assembly of claim 1, additionally having an aspiration motorcomprising a multi-lobed vacuum pump that provides a consistent, highlevel of aspiration during operation of the interventional catheterassembly.
 5. An interventional catheter assembly of claim 1,additionally having an aspiration system comprising a plurality ofvacuum pumps connected in series.
 6. An interventional catheter assemblyof claim 1, wherein the control pod incorporates a guidewire brakeoperable to clamp a guidewire in a stationary position when engaged andto allow translation of the guidewire through the brake when released.7. An interventional catheter assembly of claim 1, wherein the controlpod incorporates a selection switch allowing the operator to change thedirection of rotational output of the drive system.
 8. An interventionalcatheter assembly of claim 1, wherein the control pod incorporatesselectable operator adjustment features allowing an operator to increaseand decrease rotational speed delivered to the drive shaft.
 9. Aninterventional catheter assembly of claim 1, wherein the operating headhas advanceable, rotatable cutter surfaces at or near a distal end. 10.An interventional catheter assembly of claim 1, additionally comprisingcontrol circuitry for inactivating power to the operating head when thecurrent level required to maintain a desired rotational speed at theoperating head exceeds a predetermined value.
 11. An interventionalcatheter assembly of claim 1, wherein the drive shaft, the cathetersystem and an aspiration conduit traverse the control pod.
 12. Aninterventional catheter assembly of claim 1, wherein the actuator isslidable over the catheter system.
 13. An interventional catheterassembly of claim 1, additionally comprising control circuitry providinga delay between the time the drive system and aspiration systems areinactivated, such that the drive system may be inactivated immediatelyupon actuation of a switch, while the aspiration system may beinactivated after a delay period following actuation of the drivesystem.
 14. An interventional catheter assembly of claim 1, additionallycomprising an operating head drive motor coupled to the drive shaft,wherein the drive motor comprises a variable speed drive motor thatdelivers a constant voltage for any specified rotational output.
 15. Aninterventional catheter assembly of claim 14, wherein the currentdelivered to the drive motor is adjusted, under load conditions, if thevoltage for any specified rotational output is insufficient to producethe specified rotational output under load conditions.
 16. Aninterventional catheter assembly of claim 1, wherein the operating head,catheter system and control pod are provided as a sterile, disposablekit.
 17. An interventional catheter assembly of claim 16, additionallycomprising a fluid receptacle in fluid communication with the cathetersystem.
 18. An interventional catheter assembly of claim 1, additionallycomprising a console unit incorporating system control and displayfeatures and a motor providing vacuum for aspiration to the catheterassembly.
 19. An interventional catheter assembly of claim 18, whereinthe console unit is in electrical communication with the control pod andprovides power to the drive system.
 20. An interventional catheterassembly of claim 18, wherein the console unit displays outputoperational information including at least three of operating headrotation rate, operating head advance rate, aspiration rate, elapsedtime of operation, aspiration volume, and fluid flow rate at the targetsite.